Hi,
I’ve run into a problem on nightly 57 with this add-on. Not sure if today’s nightly update contributed, as I just installed the extension last night. When I disable it, Disqus sign in completes. I did notice a previous problem on GitHub page with sign in to twitter. Could not find link to notify developer, without registering on GitHub.
Previously using Canvas Blocker on Firefox 55. Shape Shifter is the alternative I found.